Heavy quark production in the semihard QCD approach at THERA

In the framework of the semihard ($k_T$ factorization) QCD approach, we consider the photoproduction of D* mesons associated with two hadron jets and the D* production in DIS at THERA conditions with the emphasis on the BFKL and CCFM dynamics of gluon distributions. In the photoproduction of D* mesons the attention is focused on the variable $x_\gamma$, which is the fraction of the photon momentum contributed to a pair of jets with largest $p_T$. We show that our theoretical results are sensitive to the BFKL type dynamics which may be investigated at THERA energies. We also discuss possible effect of \J/\psi meson spin alignement, which is thought to be a vivid manifestation of gluon off-shellness.Comment: 9 pages, 3 figures, in "The THERA Book", DESY-LC-REV-2001-06

TMD parton densities in associated real and virtual photon and jet production at LHC

We study the associated production of real (isolated) or virtual photons (with their subsequent leptonic decay) and hadronic jets in proton-proton collisions at the LHC using the $k_T$-factorization approach of QCD. The consideration is based on the off-shell quark-gluon QCD Compton scattering subprocesses. In the case of virtual photon production, the contributions from Z boson exchange as well as gamma*-Z interference with the full spin correlations are included. The transverse momentum dependent (TMD) quark and gluon densities in a proton are determined from the Kimber-Martin-Ryskin prescription or Catani-Ciafoloni-Fiorani-Marchesini (CCFM) equation. In the latter, we restricted to the case where the gluon-to-quark splitting occurs at the last evolution step and calculate the sea quark density as a convolution of the CCFM-evolved gluon distribution and the TMD gluon-to-quark splitting function. Our numerical predictions are compared with the recent experimental data taken by the ATLAS Collaboration. We discuss the theoretical uncertainties of our calculations and argue that further studies are capable of constraining the TMD parton densities in a proton.Comment: 11 pages, 4 figures. arXiv admin note: text overlap with arXiv:1402.549

On the possibility to detect the Higgs decay H→bbˉH\to b\bar b in the associated Z+bbˉZ + b\bar b production at the LHC

We investigate the possibility to detect the scalar Higgs boson decay $H\to b\bar b$ in the associated $Z$ and $b\bar b$ production at the LHC using the $k_T$-factorization QCD approach. Our consideration is based on the off-shell (i.e. depending on the transverse momenta of initial quarks and gluons) production amplitudes of $q^* \bar q^* \to Z H \to Z q^\prime \bar q^\prime$, $q^* \bar q^* \to Z q^\prime \bar q^\prime$ and $g^* g^* \to Z q^\prime \bar q^\prime$ partonic subprocesses supplemented with the Catani-Ciafoloni-Fiorani-Marchesini (CCFM) dynamics of parton densities in a proton. We argue that the $H \to b\bar b$ signal could be observed at large transverse momenta near Higgs boson peak despite the overwhelming QCD background, and point out an important role of angular correlations between the produced $Z$ boson and $b$-quarks.Comment: 11 pages, 6 figure